KABUL - Taliban militants on Thursday claimed victory after the US military withdrew this week from a rebel-infested area in eastern Afghanistan that became known as the "Valley of Death".

Troops pulled back from Korengal, a rugged mountainous region in Kunar province bordering Pakistan, as part of what NATO's International Security Assistance Force (ISAF) said was its new "repositioning" strategy.

The commander of foreign forces in Afghanistan, US General Stanley McChrystal, is looking to concentrate his counter-insurgency campaign against the Taliban in more populated areas.

"The move does not prevent forces from rapidly responding, as necessary, to crises there in Korengal and in other parts of the region, as well," ISAF commander General David Rodriguez said in a statement.

But an Afghan defence official said withdrawal could play into the hands of the Taliban, who have been fighting an increasingly deadly war against the foreign forces who ousted them from power in late 2001.

"Not only Korengal but any area that is abandoned is good for the Taliban.

The enemy benifits from it. They can mass there, they can benifit from the population there," the official told AFP, requesting anonymity.

The Taliban, the main insurgent group that controls several districts in southern and eastern parts of the country, were quick to seize on the US withdrawal, after years of fierce fighting in the sparsely populated valley.

"It's a great victory for us," Taliban spokesman Zabihullah Mujahed told AFP by telephone from an undisclosed location.

"The area is very, very important for us. Its mountains provide us a good hideout, it can be used as a training ground and lead our operations across the region from there," he said.

"US troops fled under our constant attacks."

The withdrawal coincides with a gradual increase in foreign forces in Afghanistan before a planned military push against the Taliban in their spiritual heartland of Kandahar, in the south of the country.

Troops levels are expected to increase from the current 126,000 to 150,000 in the coming months.